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Someone should make a double front sprocket for popular scooters

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David James

started a topic
about 1 year ago

I had the idea that someone should make a double front sprocket for popular scooters that have chain tensioners. For example, a 9 tooth and an 13 tooth somehow connected together. The idea is you can select either the low or the high range depending on what you are doing. For offroading, extended range, heavier riders, uphill..., the low range can be selected. For more speed, lighter riders, pavement only riding... the higher range could be selected. The chain length would work for both combos. It might also be a good idea that future scooters have a slightly longer motor shaft to sprocket center distance so the slight angle of the chain (from straight) using the dual sprockets is lessened.

Of course, you could not change this on the fly, but it would be useful for when you need dual "gearing". Just pull over, select the different sprocket, and then continue riding.

An extension of this idea (and to help keep the chain better aligned), would be to also have dual rear sprockets as well. The sizes could be chosen so the chain length requirement for both are the same. For example, 13-65 and 9-68. According to the chain length calculator, those 2 sprocket combos can both use the same chain length. Assuming the "taller gearing" made the scooter go 15 MPH, the "lower gearing" would make it top out at about 10 MPH (2/3rds). This would make the scooter more versatile.

If someone needed a more radical difference between the 2 ranges. they can choose sprocket combos with a greater difference in size. For example, 16-80 for the upper range and 9-84 for the lower range. This could be used for top speeds of 15 MPH and 8 MPH respectively.

Of course the chain tensioner for this setup would need to be wide enough to handle both sets of sprockets..

Even if nobody ever makes and markets this product, someone here can make their own and try it. I think it is a good idea. Not an easy mod but it would be slick and fun. You would need some welding skills, perhaps need to widen the rear "dropouts, and somehow widen the chain tensioner for the 4 sprocket setup.

The dual front sprocket only idea seems simpler to get working, especially if some retired machinist looking for a fun project would make and sell these. If the motor shaft is too short to accommodate dual sprockets with the retainer nut, perhaps the person that welds these 2 sprockets together (spaced of course), can also bundle in a strong half width sprocket retainer nut to give us a better chance of getting it to work.